Stormwater can be a form of diffuse or non-point source pollution. It can entrain pollutants, such as garbage, sediment, organic matter, heavy metals, and organic toxins, and flush them into receiving water bodies. As a consequence, natural bodies of water that receive stormwater may also receive pollutants.
In an effort to address the environmental problems posed by polluted stormwater, traps and filters for stormwater have been developed.
Stormwater filtration cartridges, such as those described in U.S. Pat. Nos. 5,707,527, 6,027,639, 6,649,048, and 7,214,311, pull stormwater through a filtration bed that removes pollutants prior to discharge into a receiving water body. Improvements to such cartridges have produced highly effective filters that allow for significant throughput, as described in the references cited above, while also allowing for easy installation and replacement of the modular cartridge units.
Another known method of stormwater filtration involves the installation of horizontally-disposed filtration beds using a mixture of materials often including organic compost. Stormwater runoff directed into these beds is filtered in an action not unlike natural soil. Live plant material is sometimes added to take advantage of its pollutant uptake as well as for aesthetic value. While mixtures for these filtration beds can be developed that accommodate a higher throughput of stormwater than natural soil, the level of throughput is still limited by the area of the bed and nature of the filtration bed material. Additionally, in areas where rainfall is sporadic, the stormwater received may not be sufficient to maintain the live plant matter therein.
It would be desirable to develop a contained, aesthetic stormwater treatment system using a filtration bed including live plants that nonetheless allows for higher throughput when necessary and adequate filtration of that higher throughput to the extent practical.
It would also be desirable to develop a stormwater treatment system that can maintain the live plants therein during periods of low rainfall without excessive irrigation needs.
Additional desired improvements to stormwater treatment systems with live plant matter include methods to easily place and later remove plant matter suitable for ground cover, and supplemental beds that expand the area of treatment and can accommodate the extended root systems of the live plants found in the filtration bed.